The present invention relates to a car stereo generally provided on the dashboard of a motor vehicle, more particularly to a car stereo having a detachable grille.
With an increase in the use of sophisticated car stereo in recent years, there have been more and more theft concerning car stereo. Such theft are supposed to have happened due to a clear appearance of a grille having various operation pushbuttons which enables a thief to quickly recognize the existence of a car stereo. In order to prevent theft of a car stereo from increasing, a car stereo having a detachable grille has been developed and become commercially available. If a car driver releases the grille from the stereo body when leaving his car, the theft may be prevented since it is difficult to know there is a car stereo provided on the dashboard.
FIG. 9 shows the above-mentioned conventional car stereo wherein a grille 20 having various operating pushbuttons is detachable from a stereo body 10. As shown in FIG. 9, the stereo body 10 has a recess 11 into which the grille 20 is mounted. The recess 11 is provided with a connector member 12 on the right hand side thereof, an elongated cassette opening 14 on nearly central portion thereof, and a detecting switch 15 on the left side of the opening 14. The detecting switch 15 is provided to detect whether or not the grille 20 is mounted on the stereo body 10.
Also, as shown in FIG. 9, the grille 20 has, on the front face thereof, a series of operating pushbuttons 22, display 23 for indicating various information such as time and a radio receiving frequency. On the upper portion of the front face of the grille 20, there is provided an elongated cassette opening 24 corresponding to and communicating with the elongated opening 14 formed on the recess 11 of the stereo body 10.
FIG. 10 shows an inner structures of the grille 20 and the stereo body 10 respectively and an electrical relationship between these two. As shown in FIG. 10, the connector member 12 is provided with various contacts including a contact 12a for obtaining 5 V electric power supply, a contact 12b for data input and output, a contact 12c for obtaining 8 V electric power supply, and an earth contact 12d. The contact 12a is connected to 5 V electric power supply circuit 17, and the contact 12c is connected to 8 V electric power supply circuit 18. The contact 12b is connected to a micro-computer 19.
Also, as shown in FIG. 11, on the rear face of the grille 20 is provided a plug member 21 which is to be connected with the connector member 12 provided on the stereo body 10. The plug member 21 has a contact 21a corresponding to the contact 12a for obtaining 5 V electric power supply, a contact 2lb corresponding to the contact 12b for data input and output, a contact 21c corresponding to the contact 12c for obtaining 8 V electric power supply, and an earth contact 21d corresponding to the earth contact 12d provided on the connector member 12. The contact 21a and contact 2lb are connected to another micro-computer 25 which, in accordance with operating modes of the various pushbuttons 22, produces control signals for indicating various information such as time and a radio receiving frequency. Further, a display driver 26 controls the operation of the display 23 in accordance with a control signal fed from the micro-computer 25. In addition, an illuminating lamp 27 is connected to the contact 21c.
The grille 20 may be attached to the stereo body 10 by first pushing the rear left end portion of the grille 20 into the left side portion of the recess 11 of the stereo body 10, and then pushing the rear right end portion of the grille 20 into the right side portion of the stereo body 10. Meanwhile, the detecting switch 15 is abutted by the rear left end portion of the grille 20 so as to become in ON state, thereby detecting the attachment of the grille 20. Then, the micro-computer 19 feeds control data through the data output contact 12b to the grille 20.
After the attachment of the grille 20 to the stereo body 10, the connector member 12 provided on the stereo body 10 becomes engaged with the plug member 21, so that an electric power of 5 V is supplied through the contacts 21a and 12a to the micro-computer 25. After the micro-computer 25 performs a reset operation, the micro-computer 25 receives a control data which is fed through the contacts 12b and 2lb from the micro-computer 19, thereby enabling the display driver 26 to perform proper operations in accordance with the control data fed thereto.
On the other hand, upon detachment of the grille 20 from the stereo body 10, the detecting switch 15 returns to OFF state. This OFF state is detected by the micro-computer 19 which at once stops feeding of the data to the contact 12b.
However, in a conventional car stereo having a detachable grille, the connector member 12 provided on the stereo body 10 and the plug member 21 provided on the grille 20 are constructed as shown in FIG. 11 which cause some problems as discussed hereinafter.
First, it is seen from FIG. 11 that said contacts 12a-12d are all in an exposed state. Since these contacts are formed of a kind of torsion spring, they have a low resistance to torsion and are easy to suffer from a deformation due to an external force in their lateral direction. Second, since the connector member 12 is engaged with the plug member 21 only when the grille 20 is attached to the recess 11 of the stereo body 10, if the attachment is performed in an inappropriate manner, an aberration is apt to occur while the contacts 12a-12d of the connector member 12 are being engaged with the corresponding contacts 21a-21d of the plug member 21. And, if an external force is unduly applied to the contacts 12a-12d on the connector member 12, the contacts 12a-12d will be deformed, hence causing an imperfect contact between the contacts 12a-12d of the connector member 12 and the contacts 21a-21d of the plug member 21.
Moreover, as shown in FIG. 3, since the contacts 12a-12d are in an exposed state after the grille 20 is released from the stereo body 10, some insulant substances such as oil is apt to be depositted onto the surfaces of the contacts due to an accidental touching. This also causes an imperfect contact between the contacts 12a-12d of the connector member 12 and the contacts 21a-21d of the plug member 21.
In addition, since the contacts 21a-21d of the plug member 21 are pressure-contacted by the contacts 12a-12d of the connector member 12, the vibration of a travelling motor vehicle will produce an external force applied on to the contacts, causing an aberration in the pressure-contact relationship and hence resulting in a deformation of the contacts which leads to a similar imperfect contact.